Protective system for power lines



PROTECTIVE SYSTEM FOR POWER LINES Filed Jan. 21, 1935 2 Sheets-Sheet 1 Aug. l8, 1936. F. HUNT 2,051,378

PROTECTIVE SYSTEM FOR POWER LINES Filed Jan. 2l, 1955 2 Sheets-Sheet 2 CTI Patented Aug. 18, 1936 UNITED STATES PATENT OFFICE 10 Claims.

This invention relates to a system of protection for electrical transmission or distribution lines and has particular reference to a system suitable for and effective as applied to complex distribution systems, and it is a general object of the present invention to provide a protective system which is dependable, sensitive, and rapid in detecting phase to phase and also phase to ground faults.

My present invention is an improvement upon that general type or form of protective equipment which is the subject of Letters Patent of the United States No. 1,940,303, entitled System for power line protection, issued December 19, 1933, to Lloyd F. Hunt and Fred B. Doolittle, and Patent No. 1,965,896, entitled System for power line protection, issued July 10, 1934 to Lloyd. F. Hunt and Fred B. Doolittle.

In the .distribution of electrical energy, that is, in the operation of a power transmission line or system, it is necessary to protect the system and units of equipment connected therewith against fault conditions as, for instance, against phase to phase faults and also against phase to ground faults. Phase to phase faults may be dependably and successfully handled through protective systems such as those which are the subject of the patents above mentioned and in the case of certain types of systems as, for instance, radial feeder systems effective protection against phase to phase and phase to ground faults can be gained by a system such as I set forth and claim in my co-pending application entitled Protective system for electrical distributing system led on even date herewith.

My present invention provides a protective system employing the general principles set forth in the above mentioned patents for protection against phase to phase faults and provides also effective, dependable protection against phase to ground faults. The present invention is applicable to systems having interconnected feeders, that is, to systems such as are commonly known as complex systems. In the following disclosure of the invention, I will describe it as applied to a loop system, and I will make detailed reference to a typical form and embodiment of the invention and to typical conditions that the invention Will handle.

It is a primary object of the present invention to provide a system of line protection suitable for use in protecting a complex system and which is effective in detecting phase to phase and also phase to ground faults without cascading time delay as is ordinarily employed in protective systems intended for the class of use for which the present invention is designed.

Another object of this invention is to provide improvements in a system of the general type set forth in the patents above mentioned, whereby 5 such system includes effective, dependable and sensitive ground detection means, including directional means making the system applicable to a complicated distribution system.

The various objects and features of this invention will be best and more fully understood from the following detailed description of a typical form of the invention applied to a complex distribution system of the loop type throughout which description I make reference to the accoml5l panying drawings in which:

Fig. 1 is a diagrammatic view of the loop system, generally, showing a power supply station feeding a loop which includes a plurality of line sections connected by sub-stations, and Fig. 2 is 20 an enlarged, detailed, diagrammatic view of a unit of equipment such as is provided by the present invention at each end of each line.

The loop system which I have illustrated for. the purpose of facilitating an understanding of the present invention includes, generally, a main station or power supply station designated generally as A, a. plurality of sub-stations C, D, E, and F connected with the supply station A and with each other by lines G, H, I, J, and K. The lines and sub-stations are connected in series and with the main supply station A to form a complex system of the loop type.

The system of the present invention is applied to or embodied in the loop or sectional system illustrated in the diagram Fig. 1, so that it will function to cut out aline section on which a fault occurs without disturbing the other sections of the system. The invention provides, generally, a

unit X of the protective system at each end of 40y each line section, which units are suitably related or interconnected, as will appear from the following description so that they function to selectively disconnect a, faulted line section Whether the fault be a phase to phase fault or a phase to ground fault. The several units X embodied in the system may be alike or, in fact, identical, and, therefore, I will lproceed with a detailed description of the construction and operation of a single unit X, it being understood that such description may apply equally to each unit X included in the entire loop system.

The portion of the system of the present invention which functions to protect against phase to phase faults may employ the general inventions which are the subject of the patents above identified.

Each of the lines, G, H, I, J, and K entering into the system includes main conductors I8, II, and I2, the circuit being a three-phase circuit. The three main conductors I9, II, and I2 of each line extend to` and connect with the bus bars I3, I4, and I5 of the stations connected by the lines.

Each unit X is connected at the end of one of the lines connecting adjacent stations whether they be sub-stations or a sub-station and the main supply station and includes the general combination and arrangement of elements that I will now describe.

Each unit X as shown in Fig. 2 includes a circuit breaker |6 connected in the main lines lll, and I2 immediately ahead of the connection of such lines with the bus bars I3, I4, and I5. The circuit breaker may be adapted for operationby suitable power as, for instance, it may be connected. for operation by current from a source independent of the system carried by lines I1 and I8 connected with power lines I3I and |32. The breaker operating circuit includes a plurality of relays which control said circuit and are governed by other elements of the unit as will be hereinafter described. I have illustrated three short time delay over-current phase relays I9, 26, and 2| and ground relay 3| connected in the breaker operating circuit so that the closing of any one ofY said relays completes the circuit and results in operation of the cir cuit breaker. The relays I9, 26, and 2| have normally opened contacts I9a, 28a and 2Ia, respectively, for controlling the circuit to the circuit breaker I6.

Transformers 23 and 24 are connected with the bus bars and conductors I0, II, and I2 to be energized by the main power circuit. Transformer 23 is a potential' transformer and transformer 24 is a current. transformer. A directional relay 25 responsive to direction of threephase power iiow is connected with the transformers and with fast overcurrent relays 26, 21, and 28. A transmitting relay 29 is operated by the relays just mentioned to start operation of a single transmitter T and to energize the coil of a lock-out relayy 3|). The transmitter T is controlled through contacts 96 and 91 whilev the coil of relay 38 is controlled through contacts 96 and 99. The closing of the contacts of the lockout relay 30 cuts out relays I9, 20, 2| and a ground relay 3| by short-circuiting the winding of relay I9 through contacts |84 and |91, and relay 261 through contacts |04 and |66, and by short-circuiting the winding of relay 2| through contacts |65. and |61, and by opening the circuit of one of the torque windings of relay 3| through contacts |29 and 284.

The potential transformer 23v has primary windings 321 and 33 suitably connected with the bus bars of theV stationand has secondary Windings 322v and 33?" energized from the windings 32 and 33, respectively, and connected with the directional relay 25 by suitable connections 39, 46, and 4 I. Connectionv 49 is'grounded.

The current transformer 24 includes secondaryy windings 24a, 24h, and 24C related to the main lines I0, |=I;,. and I2, respectively. One pole of each windingfis connected to a common line 42 which extends to the, relayv 3| which will be hereinafter described'. The other poles of the windings. 2.43; Zlib, and 24c are connected with lines. 43; 44;.and. 45,v respectively, Which connect to current coils of relay 25 as will be hereinafter described.

'Ihe power directional relay 25 includes, generally, a unit 46 mounted for rotation, which unit carries discs 41 and 48 and a contact 49. The contact 49 is connected with a line 50 and is adapted to cooperate with a Contact 5| connected by a line 52 with a terminal 52EL at the group of relays 26, 21, and 28. Rotation of tne unit 46 is damped by a fixed iield element 53 suitably related to the disc 41, and the direction of torque on the unit 46 is governed by windings 54 and 55 related to the disc 41 and windings 56 and 51, 58, and 59 related to the disc 48. One pole of the Winding 54 is connected with the transformer winding 24a by connection 43, While the other pole of the Winding 54 is connected by connection 66 with one terminal of the winding 13 of the relay 26. One pole of the winding 55 is connected by line 39 with ransformer 23 while the other pole of the winding 55 is connected by a. common connection 39a with a pole of winding 59 and a pole of winding 51. One pole of the winding 56 is connected with transformer Winding 21|c by connection 45,

while the other pole of the winding 56 is connected by connection 63v with one terminal of the winding 9| of the relay 28. One pole of the winding 56 is connected by connection lllv with transformer winding 24h, while the other pole of I winding 58 is connected by connection 64 with one pole of the winding 19 of relay 21. One pole of Winding 59v is connected by connection 48 with potential transformer 23 while the other pole of winding59 is connected by the common connection 392L with a pole of Winding 55 and a pole of winding 51. One pole of winding 51 is connected by connection 4| with transformer 23.

The relay 26 is a fast or instantaneous overcurrent relay including stationary contacts 1Q and 1I and a. movable contact 12 controlled by winding 13. The contact 15 is connected with terminal 52a which is connected with contact 5| of relay 25 by connection 52, while the ccntact 1| is connected with terminal 8| which is connected by line 82 with one pole of winding 64 of relay 29. One pole of relay winding 'i3 of relay 25v is connected by line 14- with terminal I64 of relay 36. 'I'he terminal |84 is connected by a line 15 with one pole of winding I9b of relay I9.

The relay 21 is a. fast or instantaneous overcurrent relay including stationary contacts 15 and 11, a movable contact 18 and a Winding 19 controlling the contact 18. The contact 'l5 is connected with terminal 52a, which in turn is connected with contact 18 of relay 25, while contact 11 is connected with terminal 8|, which in turn is connected with contact 1| of relay 29. One pole of winding .19 is connected with the line 64 from relay 25 while the other pole is connected with terminal |66 of relay 39 by a connection 85. Terminal I 69 is connected by line a with one terminal of winding 261 of relay 26.

is in turn connected by a line 95 with one terminal of winding 2|b of relay 2|.

'I'he transmitting relay 29 includes stationarx7 contacts 96, 91, 98, and 99, a movable contact |00 and a winding 84 controlling the contact |00. The contacts 96 and 91 are connected with transmitter T by connections' |0| and |02, respectively, and are energized upon actuation of the contact |00. Contact 98 is connected with power line |32 by connection 99b while contact 99 is connected with winding |08 of relay 39 by line 96a for completing the circuit between Winding |08 of relay 30 and power line |32 upon actuation of the contact |09.

The lock-out relay 30 includes the contacts |04, |05, |06 and |01, hereinabove referred Vt0, and a movable element |012 controlled by winding |08. One pole of the winding |98 of relay 30 is connected by line 99a with contact 99 of relay 29 and by line |08a with receiver R, while the other pole of winding |08 is connected with line I1.

The means provided by the present invention designed primarily to be responsive to phase to ground fault conditions includes, generally, a grounding transformer |20, the relay 3| hereinabove referred to, and a ground over-current relay |2|.

The ground over-current relay |2| includes contacts |22 and |24, a movable element |25 for cooperation with the contacts and a coil |26 for controlling the element |25. Contact |22 is connected by a line |28 with a contact |29 of relay 30 and is connected with movable contact |30 of relay 3| by line |33. Contact |24 of relay |2| is connected with terminal 8|, hereinabove referred to. The winding |26 of relay 2| has one pole-connected by a line |35 with one pole of the transformer winding |31 energized from the transformer |20. The other pole of winding |26 is connected by a line |38 with the terminal |39 of relay 3|.

The grounding transformer |20 is shown connected with the bus bars I3, I4 and |5 and in the form illustrated includes three primary windings |40, each having one pole connected with a bus bar and the other with a common ground connection |4|. The secondary windings |42 of the ground transformer are connected in series and in a circuit carried by a line |44 which energizes the winding |31.

The relay 3| provided by my invention is related to the grounding transformer to be responsive to ground current which may result from a fault from one phase of the power line to ground and is connected with the current transformer 24 for the detection of the direction of the fault.

The relay 3| includes a movable directional element |50 carrying contact |30, above referred to, and a disc |5|. Rotation of the disc |5| is damped by a fixed eld element |52 suitably related to the disc. Rotation of the `disc |5| is effected through windings |53 and |54 suitably related to the disc. The winding |53 has one pole connected by line 42 with the winding of current transformer 24. The other pole of winding |53 is connected by a line |56 with terminal |01 of relay 30. Line |56 connects with a line |51 which connects with one terminal of winding 2Gb of relay 20. The windings of relays |9, 29 and 2| have a common connection |60, as clearly illustrated in Fig. 2. The winding |54 of relay 3| has Vone pole connected by a line |6| with one pole of a winding |62, as will be hereinafter described. The other pole of winding |54 is connected by 'a connection |63 with terminal 1 |39 `of the relay 3|. The movable Contact |39 of relay 3| when operated in one direction cooperates with contact |65 and when moved in the other direction cooperates with contact |66. Contact |65 vis connected with terminal |61 of relay 3|, which is connectedwith line |99. Line is connected to line |9| which-in'turn is connected to line |32. The contact |66 is connected by Vline |68 with one terminal of a winding |69, hereintionary contact |89 which is connected by line |90 with a lineV |9| which connects lwith connection 50 of relay 25 and with line |32 from the source used to operate the breaker and with contact 98 of relay 29 and with the receiver R. The

rotation vof the disc |82'is effected by the inductive relationship of windings |69 and |62 which produces energization of winding 200, the winding 200 being operable to turn the disc |62. The Winding |62 has one pole connected by a line 29| with transformer winding |31 and has the f other pole connected by line |6| with winding |54, above described. "Ihe winding |69 which is related to the winding |62 has one pole connected by connection |68 with contact |66 and has the other pole connected with one pole of winding 200.

The other pole of winding 200 is connected by a line 293 with a contact204 in relay 30.

In addition tothe units and elements hereinabove referred to, the system of the present invention includes a transmitter T and a receiver R in each unit X through which a suitable interconnection is established between the two units X at the ends of a line section. The interconnection may be established Vin any suitable manner, for instance, it may be arwired connecf tion or, as I have indicated in the diagram, it may be a wired radio connection carried by the line being protected.

The transmitter T and the receiver R have one pole connected to ground through a suitable grounding connection |29 and the other pole connected with one of the lines, for instance, with line through a connection |2|EL provided with a coupling capacitor |229, the line being provided with a radio frequency trap |23 between the point of connection of line I2!a and the busses. With the arrangement just described, tbe transmitters and receivers of the units X at the two ends of each line section are connected for cooperation one with the other and are isolated or separated from the transmitters and receivers of-v the other units X of the system so that a signal sent by any one unit operates only the receiver at the opposite end of the section. Having set forth a typical form of embodiment of my invention, I will now describe its operation under certain more or less usual conditions. f

In Vthe case of a phase to phase short on one of the line sections, the current transformer at each end of that line section is energized and the units X at both ends of that line section function the same and as follows. The current transformer Y24 being connected with the operating windings of relay 25, Vas I have above described,

causes operation of relay 25 so that contacts 49 and 5| open. The energizing or operating windings of relays 26, 21, and 28 being connected in series to the relay 25 through the connections that I have described the relays 26, 21, and 28 are operated and as a result thereof relay I9 and/or relay 2E) and/or relay 2| operates. The relays I9, 26, and 2| being connected with the control or operating means of the breaker I6, the breaker is tripped out or operated when relay I9, 26, or 2| operates. In general, when a phase to phase fault occurs, one or more of the relays I9, 20, or 2| are operated through relays 25 and 26, 21 and/or 28 to trip or operate the breaker I6, this operation occurring because of the fact that the contact 49 of relay 25 is out of engagement with contact 5I.

In the event of a phase to phase short o-n the system located on the bus side of transformer 24, the current from the transformer 24 is reversed in the relays so that the contact 49 of relay 25 engages contact 5|. This phase to phase short circuit will cause any one or more of relays 21, 26, 28 to close contacts causing terminals 52a and 8| to be connected together. Closing of contact 49 and contact 5| closes the circuit to relay 23 by connections 52, 82, I3I, 50, |9I, and |32, as hereinabove described. Operation of relay 29 closes contacts 96 and 91 which control the operation of transmitter T. Transmitter T being put in operation sends a signal over the line to the receiver R of the unit at the opposite end of the line. The operation of relay 29 also causes operation of the lock-out relay 30 through closing of the contacts 98 and 99 of the relay 29. When the lock-out relay 30 is operated it shorts or cuts out the windings of relays I9, 29, and 2| and thus prevents the system from operating to trip the breaker I6. When a signal from the transmitter T is received by the receiver R of the unit X at the opposite end of the line, the contact |34 of that unit X is closed and its relay 33 is operated as a result of the connections above described. When the cut-out relay 30 is operated, the windings of the relays I9, 20, and 2| are shorted or cut out to prevent operation of the breaker I6.

From the foregoing outline of operation, it will be apparent that if a phase to phase fault occurs on a line ofthe system, the units X at the ends of that line function so that their breakers open, whereas when now occurs in a line as a result of a fault on another line of the system, the unit X receiving such flow cuts out or becomes locked so that its breaker does not function, and it initiates a signal which is carried by its line to the unit X at the other end of the line, which signal results in the unit X at the said other end of the line locking out so that its breaker does not function.

In the case of a phase to ground fault on aline, the magnitude of flow resulting from such fault is generally insuicient to operate relays 25, 26, 21, 28, I9, 20 and 2| as hereinabove described, but is suicient when aided by the current from the ground transformer |26 through transformer |31 to operate the directional element |5| of relay 3|. A phase to ground fault on a line causes the flow in relay 3| of the unit at the end of the line to be such as to close contacts |30 and |66, which causes energization of winding 200 of relay 3| through induction from winding |62 to winding |69. Energization of winding 260 results in closing of contactsv |8.| and |89 which,

through the connections |32, |9|, |96, |84, I8, I1, and I3 I results in tripping of the breaker I6.

If the phase to ground fault is on the bus side the action of relay 3| is the same as I have described except that current in winding |53 is reversed, causing contact |30 to close with contact |65. Closing of contact |30 with contact |65 closes the circuit to relay 29 through contacts |22 and |24 of relay |2|. Relay |2| is energized from transformer |31 through line 20|, Winding |62 and |54 of relay 3|, line |38, and line |35. Contacts 96 and 91 of relay 29 close the circuit to transmitter T with the result that a signal is sent to the unit X at the other end of the line section to lock it out. Under the condition of operation just described, contact |36 of relay 3| is out of engagement with contact |66 thereof, and, therefore, winding 266 is not energized, and, therefore, contacts |8I and |89 of relay 3| do not close, and,

therefore, the breaker I 6 of the unit X cannot trip. In the event that a signal is received relay 3Q is energized, opening contacts |29 and 264 which control the circuit through the winding 290. When the winding 206 is thus cut out so that it cannot be energized, the unit X is locked out so that its breaker I6 does not trip.

Having described only a typical preferred form and application of my invention, I do not Wish to be limited or restricted to the specic form and application herein set forth, but wish to reserve to myself any modications or variations that may appear to those skilled in the art or fall Within the scope of the following claims:

Having described my invention, I claim:

l. A protective system for a sectional current carrying line including, protective units connected with each end of a line and each including a circuit breaker controlling the line, operating means for the circuit breaker, a lockout relay operable to lock out the operating means of the breaker, and means including two movable elements, one a directional element operable in one direction to operate the lockout relay and in the other direction to close an operating circuit to the other element and connected with the line secing means for the circuit breaker, a lockout re a lay operable to lock out the operating means of the breaker, and means including two movable elements, one a directional element operable in one direction to operate the lockout relay and in the other direction to close an operating circuit to the other element and connected with the line section to be operated by current flow dueto a fault, and the other element connected with the line through ground to be operated by ground flow and flow in said circuit to trip the breaker.

3. A protective system for a sectional current carrying line including, protective units connected with each end of a line and each including, a ground transformer connected with the line, a current transformer connected with the line, a circuit breaker controlling the line and including an operating circuit, a lockout relay operable to lock out the operating circuit of the breaker, and means including two movable elements, one a directional element operable in one direction to operate the lockout relay'and in the other direction to close an operating circuit to the other element and connected with the line section to be operated by current ow from the current transformer due to a fault, and the other element connected with the line through ground to be operated by ground flow from the ground transformer and iiow in the last named circuit to complete the operating circuit of the breaker.

4. A protective system for a sectional current carrying line including, protective units connected With each end of a line and each including, a circuit breaker controlling the line and including an operating circuit, a lockout relay perable to lock out the operating circuit of the breaker, a signal receiver operable to actuate the lockout relay, a signal transmitter, and a ground relay including two movable elements, one a directional element operable in one direction to operate the lockout relay and the signal transmitter and in the other direction to close an operating circuit to the other element and connected with the line section to be operated by current ow due to a fault, and the other element connected with the line through ground to be operated by ground iiow and flow in the last named circuit to complete the operating circuit of the breaker. v

5. A protective system for a sectional current carrying line including, protective units connected with each end of Ya line and each including, a ground transformer connected with the line, a current transformer connected with the line, a circuit breaker controlling the line, an operating circuit for the circuit breaker, a lockout relay ope-rable to lock out the operating circuit of the breaker, a signal receiveroperable to actuate the lockout relay, a signal transmitter, and a relay including two movable elements, one a directional element operable in one direction to operate the lockout relay and the signal transmitter and in the other direction to close an operating circuit to the other element and connected with the line section to be operated by current flow due to a fault, and the other element connected with the line through ground to be operated by ground flow and flow in the last named circuit to complete the operating circuit of the breaker.

6. A protective system for a sectional current carrying line including, protective units connected with each end of a line section and each including a circuit breaker controlling the line, an operating circuit for the circuit breaker, a time delay overcurrent trip relay controlling the operating circuit of the breaker and operatively connected with a section of the line to be responsive to overcurrent in the line, a lock-out relay for the overcurrent time delay relay, means connected with the said line section whereby the lock-out relay of a unit is operated upon overcurrent iiow in a single direction in said section of the line, and a ground relay including two movable elements one a directional element operable in one direction to operate the lock-out relay and in the other direction to close an operating circuit to the other element and connected with the said line section to be operated by flow in said single direction to operate the lock-out relay and the other element connected with the line through ground to be operated by ground flow in the last named circuit to complete the operating circuit of the breaker.

7. A protective system for a sectional current carrying line including, protective units connected with each er'id`of a line "section and each including a circuit breaker controllingthe line, a time delay overcurrent trip relay controlling the breaker and operatively connected With a section of the line to be responsive to overcurrent in the line, a lock-out relay for the overcurrent time delay relay, means connected with the said line section whereby the cut-out relay of a unit'is operated'upon overcurrent now in a single direction in said section of the line, a ground transformer connected with the line, and a ground relay including two movable elements one a directional element operable in one direction to operate the lock-out relay and in the other direction to close an operating circuit to the other element and connected with the said line section to be operated by flow in said single direction to operate the lock-out relay and the other element connected with the line through ground to be operated by ground flow in said circuit to trip the breaker.

8. A protective system for a sectional current carrying line including, protective units connected with each end of a line section and each including a circuit breaker controlling the line, a ground transformer connected with the line, a current transformer connected with the line, a time delay overcurrent trip relay controlling the breaker and operatively connected with a section of the line to be responsive to overcurrent in the line, a lock-out relay for the overcurrent time delay relay, means connected with the said line section through the current transformer whereby the cut-out relay of a unit is operated upon overcurrent ow in a single direction in said section of the line, and a ground relay including two movable elements one a directional element operable in one direction to operate the lock-out relay and in the other direction to close an operating circuit to the other element and connected with the said line section to be operated by ilow in said single direction to operate the lock-out relay and the other element connected with the line through ground to be operated by ground flow in said circuit to trip the breaker.

9. A protective system for a sectional multiphase current carrying line including, protective units connected with each end of a line section and each including a circuit breaker controlling the line, a plurality of time delay trip relays controlling the breaker, connecting means connecting each phase of the line with a trip relay whereby a trip relay is operated upon overcurrent flow of predetermined duration on any phase of the line, lock-out means for the trip relays, and connecting means between said line section and the lock-out means of the units whereby the lock-out means of a unit is immediately operated upon overcurrent flow in a single direction in said section of the line, said connecting means including a ground transformer connected with the line section, a current transformer connected with the line section, and a relay including a directional element operated by current from the current transformer, and a tripping element controlled by the directional element and current from the ground transformer.

10. A protective system for a sectional current carrying line including, protective units connected with each end of a line section and each including a circuit breaker controlling the line, a time delay overcurrent triprelay controlling the breaker and operatively connected with a section of the line to be responsive to overcurrent in the line, a lock-out relay for the overcurrent time delay relay, a signal receiver operable to actuate the cut-out relay, a signal transmitter, means connected With the said line section whereby the lock-out relay and the signal transmitter of a unit are operated upon overcurrent flow in a single direction in said section of the line, and a ground relay including two movable elements one a directional element operable in one direction to operate the lock-out relay and the signal transmitter and in the other direction to close an operating circuit to the other element and connected with the said line section to be operated by flow in said single direction to operate the lock-out relay and the other element connected with the line through ground to be operated by ground ow in said circuit to trip the breaker.

LLOYD F. HUNT. 

